Longitudinal tape, such as magnetic tape for magnetic tape cartridge volumes, being a serial access media, is typically not subject to reuse until after all of the data stored on the longitudinal tape has been expired. When all of the data has been expired, the physical cartridge volume can be marked as scratch and rewritten.
Data may be stored by magnetic tape as various blocks or sections of data, arranged in a serial string ending with an “end of tape”, and also called an “end of data”. Subsequent additions of data begin at the previous “end of tape”, and continue, ultimately ending with a new “end of tape”.
Data that has been stored and subsequently modified is typically not modified in place. Rather, the updated data is stored separately at the end of the string of data and the host system identifies the superseded data as expired.
Thus, blocks or sections of data throughout the serial string of data may be expired. To attempt to reuse the expired blocks or sections would require movement of the tape back and forth to access the reused blocks or sections, resulting in an inefficient use of the tape. Hence, the reuse is not done, and the tape cartridge volume remains with the expired blocks or sections in place until all of the data stored by the tape cartridge volume has been expired, if that ever happens. As a further result, the space efficiency of the tape cartridges is underutilized.